Inject Default Values Safely with $request->mergeIfMissing()

Use $request->mergeIfMissing() in Form Requests to set default fallback parameters without overwriting user-provided values.

When handling search queries, pagination limits, or optional boolean flags, calling $request->merge() overwrites existing values.

mergeIfMissing() injects default parameters only when the key is absent from the request payload.

Using mergeIfMissing in Form Requests

namespace App\Http\Requests;

use Illuminate\Foundation\Http\FormRequest;

class FilterProductsRequest extends FormRequest
{
    protected function prepareForValidation(): void
    {
        $this->mergeIfMissing([
            'per_page' => 15,
            'sort'     => 'latest',
            'status'   => 'active',
        ]);
    }

    public function rules(): array
    {
        return [
            'per_page' => ['integer', 'min:1', 'max:100'],
            'sort'     => ['in:latest,price_asc,price_desc'],
            'status'   => ['in:active,archived'],
        ];
    }
}

Summary

Sets fallback values only when keys do not exist in the request.
Preserves explicit user inputs (including false or 0).
Keeps validation rules and controller actions clean and predictable.

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Tags: Laravel HTTP Form Requests Clean Code

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Using mergeIfMissing in Form Requests

Summary

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